Substrate recycling method

Abstract

Embodiments of the disclosure relate to a substrate recycling method and a recycled substrate. The method includes separating a first surface of a substrate from an epitaxial layer; forming a protective layer on an opposing second surface of the substrate; electrochemically etching the first surface of the substrate; and chemically etching the electrochemically etched first surface of the substrate.

What is claimed is: 
     
       1. A method of recycling a substrate, the method comprising:
 separating a first surface of a substrate from an epitaxial layer; 
 forming a protective layer on a second surface of the substrate; 
 chemically etching the first surface of the substrate; and 
 before the chemically etching of the first surface of the substrate, forming the protective layer on at least a portion of a side surface of the substrate. 
 
     
     
       2. The method of  claim 1 , wherein the protective layer includes SiO 2 , Kapton tape, or thermal tape. 
     
     
       3. The method of  claim 2 , wherein the protective layer has a thickness ranging from 5000 Å to 5 μm. 
     
     
       4. The method of  claim 1 , wherein the substrate includes a growth substrate and a sacrificial layer disposed over the growth substrate such that the sacrificial layer is located on the first surface of the substrate. 
     
     
       5. The method of  claim 4 , wherein the substrate further includes an etch-stop layer disposed between the sacrificial layer and the growth substrate. 
     
     
       6. The method of  claim 5 , wherein the sacrificial layer includes an n-type gallium nitride-based semiconductor layer, and the etch-stop layer includes an undoped gallium nitride-based semiconductor layer. 
     
     
       7. The method of  claim 6 , wherein the chemically etching of the first surface of the substrate includes removing the n-type gallium nitride-based semiconductor layer to expose the undoped gallium nitride-based semiconductor layer. 
     
     
       8. The method of  claim 6 , wherein the chemically etching of the first surface of the substrate includes remaining at least a portion of the undoped gallium nitride-based semiconductor layer. 
     
     
       9. The method of  claim 1 , wherein the separated first surface of the substrate includes protrusions and depressions, the protrusions having smoother surfaces than the depressions. 
     
     
       10. The method of  claim 1 , wherein the substrate includes a growth substrate including a sapphire substrate or a gallium nitride substrate. 
     
     
       11. The method of  claim 10 , wherein the second surface of the substrate includes N-face (nitrogen-face). 
     
     
       12. The method of  claim 11 , the protective layer covers the N-face of the substrate to protect the N-face during the chemically etching of the first surface of the substrate. 
     
     
       13. The method of  claim 1 , wherein the chemically etching of the first surface of the substrate is performed using a solution comprising NaOH or KOH. 
     
     
       14. The method of  claim 1 , wherein the chemically etching of the first surface of the substrate includes etching at least a portion of the protective layer. 
     
     
       15. The method of  claim 1 , further including removing the protective layer after the chemically etching of the first surface of the substrate. 
     
     
       16. The method of  claim 1 , wherein the chemically etching of the first surface of the substrate includes flattening the first surface of the substrate. 
     
     
       17. The method of  claim 1 , wherein the separated first surface of the substrate includes protrusions and depressions, and the chemically etched first surface of the substrate is substantially flat. 
     
     
       18. A method of recycling a substrate, the method comprising:
 providing a substrate having a surface separated from an epitaxial layer, the substrate having a stack structure including a growth substrate, an etch-stop layer, and a sacrificial layer; and 
 recycling the substrate to have an upper portion including at least a portion of the etch-stop layer including:
 performing electrochemical etching on the surface of the substrate, and 
 performing a chemical etching on a portion of the electrochemically etched surface of the substrate to remove the sacrificial layer. 
 
 
     
     
       19. The method of  claim 18 , further comprising, before the performing of electrochemical etching, providing a protective layer on at least one of an opposite surface of the substrate and a side surface of the substrate. 
     
     
       20. The method of  claim 18 , further comprising growing a semiconductor layer over the recycled substrate.